Police responding to the call set up a quadrant around the area and brought in a K-9 unit to assist with the search, but they were unable to locate the suspect.

Mission Ranch apartment managers, who did not respond to requests for a comment on the attack, appears to have sent tenants an email informing them of the alleged attack.

"Please exercise caution at all times, be aware of your surroundings, use the buddy system," the email, which was sent to mySA.com by a resident, reads. "If you see or hear anything suspicious please call 911 immediately."

Managers also distributed with the email a sketch from police of a suspected serial rapist who has been attacking women in the area.

The first reports regarding the suspected rapist came in late January, when a string of stalking and sexual assault calls were reported in the area. Police have not released the exact number of confirmed assaults in the area, but determined one suspect may be responsible for all of the reported incidents.

In prior attacks, the man was reported to be armed with a knife. Police said the suspect would scratch or knock on women's doors and then force his way inside.

The suspected serial rapist is described as a black man in his early to mid-20s who is about 5 feet 7 inches to 5 feet 11 inches tall. He weighs about 140 to 160 pounds. He has no facial hair, and he wears a bandana to cover his face.

Police say he is soft spoken and does not have an accent. He has been seen on a BMX bike but is generally on foot.

Anyone with information is asked to call police at 210-225-8477. Tipsters who wish to remain anonymous can call Crime Stoppers at 210-224-7867.

This story has been updated with a corrected date of the reported assault to reflect new information provided by SAPD.